One of my girls in my sorority (Ascari) is missing 2/3 of her dorsal fin as of this morning. It is swollen at the base and bleeding. I've had some fin nips but I am fairly certain that the other girls did NOT do this to her. When I was in my room earlier and the lights in the tanks were still off, I heard what sounded like one of the girls jumping out of the water and smacking the hood of the tank pretty good.

Do you think this could be from her jumping and hitting the lid? Daihatsu is usually my suicidal fish, not Ascari, lol. I don't know if this could even be from the other girls since it's pretty bad and Ascari is usually the one chasing the other girls around.

My main question is, do I wait for it to heal or do I need to treat is ASAP since there is an injury on her body and not just her fins?

I do have vitachem in the tank and I added a few more drops after I noticed this. There has been a few nips and tears but no rot because the water parameters are good.

Edit: I know the picture sucks but it's functional. Even with her fin looking like that, she's super active and won't stop moving around! She's not acting strangely.

Do you have another tank you can put her while she heals? If you do, separate her. Fish still fight in the dark and bettas are naturally aggressive so even if you thought one was docile --any fish can bite.

As for moving her to a QT tank, do you think she'd prefer it? I would do whatever it takes to keep her stress-free right now, so that her immune system can work on healing this. (Sororities scare me. I'd probably move her. But that may just be me. LOL)

If you keep her in the community tank, monitor the sorority closely. Make sure no one starts picking on her. They're liable to go after her open wound.

Is it possible that she was chasing someone, and got so excited the she lunged out of the water and hit the lid?

(If you really want to do something, you could put her in a QT tank with low dose aquarium salt. If you do this, monitor for signs of fluid retention or bloating. If it occurs, switch to Epsom salt.... but if there are no signs of infection and she's behaving normally, then just warm, clean water are the most important things.)

She doesn't seem to be having issues. She's pretty feisty and is acting normally. She is one of the only two girls who have NEVER had nipped fins. My purple girl and the two EE girls get the worst of it (but now I only have one of the EE girls) and the three dragon girls never had any nips until recently one got a small one on her tail, so it seemed unlikely to me that this was from the other girls.

I added stress coat to the tank a little bit ago and I already use vitachem in all my tanks. The area seems pretty swollen, though. The girls leave each other alone, at least when I'm watching, but if I had to guess who the alpha is, it's probably her or Mercy, my purple girl.